The preparation of aliphatic copolyesters was reported in the mid-1930's as described in U.S. Pat. No. 2,012,267. Since that time, there has been a tremendous amount of work done in the field of polyesters. A very high percentage of this work has been done on aromatic polyesters and copolyesters, such as poly(ethylene terephthalate) because of their high melting points, high glass transition temperatures, good barrier properties, high tensile strengths and other useful properties. There has been little commercial interest in aliphatic polyesters because of their low melting points and relatively poor physical properties.
The melting temperatures of most linear aliphatic polyesters prepared from diacids (or derivatives thereof) and diols are in the range of 50.degree. C.-70.degree. C. Melting temperatures below 80.degree. C.-90.degree. C. are generally not useful for most commercial applications due to dimensional instability upon storage in warm environments.
Two aliphatic polyesters which have unusually high melting temperatures are poly(tetramethylene succinate) and poly(ethylene succinate). Their melting temperatures are 120.degree. C. and 104.degree. C., respectively.
While, in general, aromatic polyesters have superior physical properties to aliphatic polyesters, aromatic polyesters are not rapidly biodegradable. Aliphatic polyesters, on the other hand, are generally considered to be rapidly biodegradable. For example, U.S. Pat. No. 3,932,319 broadly discloses blends of aliphatic polyesters and naturally occurring biodegradable materials. This patent also discloses evidence that several of the aliphatic polyesters are biodegradable.
Aliphatic polyesters prepared from succinic acid have been claimed as surgical articles as in U.S. Pat. No. 3,883,901. In this patent, succinate polyesters prepared from succinic acid and C2 to C6 diols to a "film- or filament-forming molecular weight" are disclosed. Also, preparation of sutures from both poly(ethylene succinate) and poly(tetramethylene succinate) are given.
Several other reports of succinate polyesters from medical applications have been made. In J. Macromol. Sci.-Chem., A25(4), pp. 467-498 (1988) by Albertson and Ljungquist, the preparation of block copolyesters of poly(ethylene succinate/poly(tetramethylene glycol) and their use as suture material was reported. In U.S. Pat. No. 4,594,407, the preparation of polyesters for medical devices from succinic, malic and fumaric acids and 1,4- and 2,3-butanediols was disclosed. U.S. Pat. No. 4,032,993 discloses surgical articles prepared from copolyesters of succinic and oxalic acids and various low molecular weight diols.